This research examines relationships among pain, everyday activities and mood states, and long-term quality of life among African American (AA; Black) and non-Hispanic White (NHW; White) older adults with osteoarthritis (OA) of the knee. Recent evidence suggests considerable divergence in the experience and effects of this potentially very debilitating disorder among AAs and NHWs. Unfortunately, there has been little in-depth research on racial/ethnic (R/E) differences previous work on racial/ethnic (R/E) disparities in basic experience of OA symptoms, and in the emotional impact of those symptoms and related disability. This research addresses that gap in a longitudinal study of OA pain, functional disability and emotional well-being of AAs and NHWs. Working from a biopsychosocial model, we shall use functional assessments, self-reports, and real-time assessments of activities, symptoms and mood states to construct a comprehensive view of how OA affects physical and emotional functioning. Specific aims are (1) to describe racial/ethnic differences in associations among pain, disability, and emotional well-being of persons with OA of the knee; (2) to identify origins of those differences in (a) biological factors such as disease process and general health, (b) social factors such as demographic characteristics, and (ii) psychological factors, including stable personal characteristics and transitory (within-day) affective, cognitive and behavioral responses to knee symptoms; (3) to use experience sampling methods (ESM) and actigraphy to investigate how racial/ethnic differences in global associations among pain, functional limitations and emotional distress are reflected in the daily lives of OA sufferers, and (4) to explore how the interplay of transitory (within-day) symptoms, activities and mood states influences long-term physical and emotional well-being. These aims will be achieved in a 5-year, multi- site project examining cross-sectional and longitudinal associations among demographic and health characteristics, OA-related pain and disability, restriction of everyday activities, and emotional well-being. A sample of 220 AA and 220 NHW adults aged 50+ with physician-diagnosed OA of the knee will complete a comprehensive baseline assessment tapping biological, psychological and social vulnerability to OA pain and its effects; objective functional limitations; pain; activity restriction, and emotiona distress. Immediately post- baseline, participants will complete a 7-day ESM procedure comprising actigraphic assessment of activity levels along with 4 daily telephone contacts to assess current symptoms, activities, and moods. One year later, participants will repeat all measures, including the ESM component, to capture changes in overall physical and emotional well-being as well as patterns of daily activity and moods. Resulting data will offer unprecedented insight into the global factors that differentiate AAs' and NHWs' experience of OA symptoms, and how daily experiences are concatenated to influence longer-term physical and emotional well-being.